Stud driving tool



April 2 1, 1964 M. HlL'rl STUD DRIVING TooL 5 Sheets-Sheet 1 'Filed Feb. 26, 1959 la, 7. 0 o w a 2 f, n f 2 r P ll r 9 A7/ //////MM7 L m L rr- 7 5 Il A 3 2 flm Y L W- 2 7.2 n y 5 Z April 21, 1964 M. HlLTl STUD DRIVING Toor.

5 sheets-sheet 2 Filed Feb. 26, 1959 April 21, 1964 M. HIL-n 3,129,429

STUD DRIVING TOOL Filed Feb. 26, 195e 5 sheets-sheet s f3 29k f3 2, 9b la.

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Filed Feb'. 2e, 1959 5 Sheets-Sheet 4 /rl-g. 2a

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STUD DRIVING Toor.

Filed Feb. 26, 1959 5 Sheets-Sheet 5 l 79 A` //7\ I 45.

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a a? 7'b 7 i NZS 2e' 'an r/ 1b y I 3 /Q 34 s y /u c l 8l i "l 5 S\ Y \\\.,sf3*/ I Z k1| |N`v-ENJTR Mar-1122 Ji'zl United States Patent Oiiice 3,129,429 Patented Apr. 2l, 1964 3,129,429 STUD DRIVING TOOL Martin Hilti, Vaduz, Liechtenstein, assignor to Anstalt fr Montage-Technik, Vaduz, principalty of Liechtenstein Filed Feb. 26, 1959, Ser. No. 795,819 Claims priority, application Germany Feb. 27, 1958 Claims. (Cl. 1-44.5)

The invention relates to stud-driving apparatus for the insertion of anchoring studs in hard materials such as stone, concrete, iron and the like. More in particular, this invention relates to such apparatus in which an expanding propellant charge exerts a force on the anchoring studs, which may be in the form of nails, bolts, etc., and may be without heads or may have heads including threaded heads.

It is known in the art to provide a stud-driving device wherein a propellant charge is used to drive an anchoring stud in such a manner that the stud is accelerated during the course of its free iiight to the point at which it is driven in. In these devices the propellant charge works directly on the anchoring stud or through a driving piston which acts as a hammer for the stud. In another type of design, the expansion of the propellant charge exerts an impact effect; that is, the charge drives a body, separated by a given distance from the anchoring stud, against the anchoring stud in such a manner that the anchoring stud is not accelerated in any free ilight. In all these devices the cartridge containing the propellant charge has a iixed position in the apparatus, and the recoil from the propellant charge acts either directly against the stud-driving apparatus or indirectly thereon through springs or braking mechanisms.

The present invention is concerned with a design for such devices in which the expansion of a propellant charge brings about the driving in of an anchoring stud without acceleration of the stud during the course of free flight. One object of the invention is the complete or virtual elimination of recoil in the apparatus. A further object of the invention is the accomplishment of the insertion of anchoring studs with the smallest possible propellant charge with consequent advantages from the viewpoint of safety, one of these advantages being that the energy unexpended at the conclusion of the driving thrust is conveniently absorbed. In this manner penetration of the hard material is eifected practically without rebounds and recoiling. Additional features of the invention are concerned with control means by which the energy released during accidental firings is harmlessly absorbed, as well as with control means which eliminate such accidental rings.

The stud-driving apparatus to be described hereinbelow is principally characterized in having the propellant charge fitted between a recoil damping piston on one side and the anchoring stud or hammer means carrying the anchoring stud on the other side. Additionally, the position of this charge along the longitudinal axis of the apparatus is adjustable.

In this manner, freely moving masses to take up the recoil within the apparatus can be proportioned in a known manner so that the reaction forces of the expanding propellant charge exerts no recoil or very little recoil against the apparatus. Use of the apparatus has shown that it is suflicient that the mass of the parts of the apparatus which move in the driving direction are in a proportion of one to ten to the mass which is set in movement by the forces of reaction. This condition or similar conditions are easily achievable during construction, for example, by iitting that end of the recoil damping piston which projects rearwardly out of the guiding tube of the apparatus with an iron cap of appropriate weight. This cap is replaceable with other caps, since experience shows that the driving process should be altered when different propellant charges are used, when different bolts are to be driven and when different conditions of resistance to penetration of the bolts are encountered. The recoil damping piston can be provided with a friction element which holds the piston in any desired position within the guide tube.

In a preferred embodiment the front face of the recoil damping piston is designed as a receptacle for the cartridge holding the propellant charge. In this arrangement the axial position of the cartridge at the moment of firing is automatically determined by the length of the anchoring stud to be driven in, or by the anchoring stud and a hammer for the stud.

Further details and advantages of the invention will be evident from the following description of the embodiments pictured in the accompanying drawings.

FIGURE l is a front view in section of a stud-driving apparatus designed for manual operation;

FIGURE 2 is a plan view in section taken along line II-II of FIGURE 1;

FIGURE 3 is a plan View in section taken along line III-III of FIGURE 1;

FIGURE 4 shows interchangeable parts of the apparatus in FIGURES 1 through 3, namely a drivable piston and a protective plate;

FIGURES 5a and 5b are plan Views partially in section showing two other embodiments for guiding an anchoring stud within the apparatus;

FIGURE 6 is a side view partly in section showing an embodiment of the apparatus having a spring-cushioned hammering mass and a release mechanism;

FIGURE 7 is a partial side View partially in section showing one means by which the propellant charge may be mounted in a driving hammer;

FIGURE 8 is a side view partially in section showing a portion of a device with movable guiding jaws positioned over the driving aperture;

FIGURE 9 is an enlarged plan view in section along line IX-IX of FIGURE 6 showing the cavity for the reception of a cartridge;

FIGURE 10 is an enlarged view of a cartridge;

FIGURES 11 and l2 show diiferent anchoring studs with perforated discs thereon;

FIGURES 13 and 14 show two positions of a safety mechanism which intercepts an anchoring stud released by accidental tiring of the propellant charge;

FIGURES 15 and 16 show another safety mechanism of this type in plan view partially in section and side view respectively;

FIGURES 17 and 18 show an arrangement for preventing deep penetration of the anchoring studs in case of accidental firing without a guide washer;

FIGURE 19 is a side view partially in section of a stud-driving apparatus with a safety mechanism in which apparatus the expanding gases released on accidental tiring escape without having substantial effect on the anchoring studs;

FIGURE 20 is a side View partially in section showing an embodiment of stud-driving apparatus in which a safety mechanism providing against accidental tiring is provided by rotating the piston accepting the cartridge and the hammer carrying the ring pin in opposite directions;

FIGURES 2l and 22 are plan views -in section taken along Ilines XXI-XXI and line XXII--XXII respectively of FIGURE 20; and

FIGURES 23 land 24 are side views partly in section of another embodiment [for preventing accidental firing, in which figures Itwo different positions of the recoil damping piston are shown.

The stud-driving apparatus shown in FIGURES 1 through 3 is comprised principally of a tubular guide 1 having a piston Z provided with enlarged lleading end 3 and free to move in the guide 1. The opposite end fiof the piston extends into closing member 5 which is provided with a friction element 6 so that the piston remains in Iany desired position. Extension of the piston out of the apparatus is prevented by the engagement between the shoulder of the piston leading end '3 and surface 40 of closing member 5. On the end of the piston which projects outwards from the apparatus is fastened a mass in the lform of an iron head or cap 7, which is replaceable by other similar caps. Closing member S can be slid down along the neck 8 of tubular guide 1 and can he fastened to the guide by a 90 degree turn tot bayonet-like wedge breech lock 9. Closing member 5 may be locked in closed position by means of ball catch lit.

In the Ifront end of the piston 2 is recess 11 for the reception of a cartridge 12 lthe base of which faces the driving direction. Recess 11 is entrant on a small-diameter closed cavity 51 into which the initial expansion of gases takes place. Because of the relationship of recess `11 and closed cavity 51 to each other, only cartridges of la specific length can be tted into 'recess 11.

A hammer 13 is mounted in tubular guide 1 in slidabie fashion in -front `oi the leading end of piston 2. In the tapered leading end 14 of the hammer is a recess for holding and centering the back end of an 'anchoring stud l5 on which perforated disc 19 is placed. Disc 19 centers stud n1S in driving aperture 20 before Land during the driving process. Hammer 13 is provided iwith iiriction elements for example spreading rings 52.

The movement of hammer 13 during driving of a stud 15 is limited by the contact of `shoulder 16, formed between hammer 13 and its leading end 14, with replaceable stop-ring 17. In the embodiment shown in FIGURE 1, this contact is designed Ito take place so that the leading end of hammer 13 can project beyond the positioning surface oi the apparatus.

For the tiring of the cartridge, the rear face of hammer 13 is provided with a broad, level, iiring pin 13, the surface area `of which covers between one-fifth and the entire base area of the cartridge, preferably about one-half this area. This avoids a sudden ignition which is undesirable in this type of device.

With apparatus as shown in `FIGURE 1, the rfollowing forces must be overcome in driving in an anchoring stud: (1) Resistance of hard material 21 to penetration by shank 15 of the stud; (2) displacement resistance exerted against perforated :disc 19, which tends -to be pressed to some degree, into material 21 by the action of hammer 13 and its leading end 14; and (3) in case the resistive forces in (l) and (2) Iabove are overcome, and residual energy still remains in the moving parts of the device, shoulder 16 of the hammer -Will strike against stop-ring 17 in the device. Together, these three forces oppose and equal the driving torce produced in the forward or driving direction by the propelling charge. This driving force is the reaction force which acts on piston 2 and massive cap 7 attached thereto.

`If the forces mentioned in (l) land (2) above are both zero (corresponding to a tfree yand -unopposed shootmg of a stud-which can have most dangerous consequences 1n prior art devices), the overwhelming; majority of the energy will be expended in the collision of hammer 13 against stop-ring 17. Only a very minimum residual energy, corresponding with the substantially negligible mass of the anchoring stud, will remain, and the stud will be driven forward with only slight force. Calculations and practical experience have shown that forces of the order of one, or at most two mkg. are involved, i.e. forces too small to produce harmful results.

The expansion volume throughout which the propellant charge is effective ladjusts itself automatically according to the length of the stud being driven, or 'to the form and size of hammer 113 driving the st-ud. Large hammers of heavy mass :are chosen to drive even small studs of minimal mass if good penetration of a very hard material is desired. In order .to obtain a uni-form tenacity for `the studs driven, short studs are used in hard materials, long studs in soft materials. rl`he device of the invention accommodates itself readily to such variations.

When in its lowest position `during a stud-driving stroke, or when nearly in such position, hammer 13 exposes exhaust apertures 22 in the walls of tubular guide 1, through which the expanding propellant passes into closed space 23 surrounding tube 1 as a jacket. Because of the expansion of the gases into a closed volume, practically all explosion noises are avoided.

Space 23 is closed on the exterior by' `shell 24, which also serves as a hand grip for the device. Shell 24 can be drawn upwards over tube 1, after removal of closing member 5 and locking pin 25, to clean space 23 of remaining explosion gases. Such cleaning is required only after a large number of explosions, however.

Firing can be initiated by a light hammer ltap against cap 7 of the piston 2. Generally the piston is thereby shoved -forward into the tiring position, though not necessarily so. lf the hammer remain-s in position on cap 7 after the blow, an increase in mass opposing the reactive force of the propellant results.

It will be evident that lche closing member 5 serves as a stop means for limiting the forward movement of the piston'Z.

'Ihe total length of piston 2 `should be so chosen that in its extreme driving position, shown in FIGURE l, it cannot push hammer 13 into a position flush with the surface of material 21. In this manner, accidental rings are avoided.

After release of closing member 5', it and piston 2 can be removed from the device and replaced with an ordinary plunger 26 (FIGURE 4) driven by hammer blows. Closing member 5 can be replaced on neck 8 with protective plate 27, which plate can be fastened in place as was member 5. It can also -be seen in FIGURE 4 that the lower end of plunger 26 has a recess 28. Such a provision avoids vdamage to tiring pin 1S on hammer 13 which might otherwise be caused.

The device also has a broad positioning base at the lower end of shell 24, and this base in the embodiment shown is constructed in two parts with base plate 2?, positionable against the surface of the hard material, removably attached by means of screws 30. Permanent magnets 31 (see also FIGURE 2) are mounted in two diametrically opposed radial cavities in base plate 29. The magnets hold stud 15 and perforated disc 19 in position before and during the driving process. In place of magnets, mechanical means can also be provided for holding disc 1g, such as springs extending in the axial direction and projecting slightly over the inner wall of driving aperture 2t). As known, the positioning base is flattened along one edge 41.

The device can be used in any position, so that, for example, aperture 20 may face down, or up as against a ceiling, or sideways against a wall. Piston 2, cap 7, hammer 13, as well as the stud used, all retain their positions until the propellant acts because of the provisions made to inhibit their movement, for example by spreading rings 52 in hammer 13.

As shown in FIGURE 6, initiation of tiring can take place other than by a hammer blow on the cap of the piston. In FIGURE 6, a posterior tubular extension 32 has mounted in it hammer-like masses 34 and 35, compressible against spring 33. This structure cooperates with trigger mechanism 37, mounted in handle 36, so that after triggering, masses 34 and 35 strike head 38 of piston 2a and thereby eiect tiring. The reaction forces, in this case, are taken up by masses 34 and 3S, and head 33. In other respects, the device in FIGURE 6 is constructed like that in FIGURE 1.

The enlarged cross section of FIGURE 9, taken through cartridge recess 11, shows that the walls of this recess deviate slightly from a circular configuration. This has the advantage of accommodating a force lit for the cartridge 12. A force fit can also be obtained by a slight expansion in the cylindrical walls of the cartridge, as shown by the broken lines in FIGURE 10.

FIGURE 7 shows that a cartridge 12 containing propellant may in some instances be mounted in a recess 39 in the end of hammer 13a that is opposite to leading end 14a. In still other cases, it is possible to eliminate the hammer in the device, in which event the cartridge may be placed directly in a recess 42 in head 43 of a stud 44, as depicted in FIGURE 8. In both of these cases, liring pin 18 is mounted on the leading end of piston 2b.

It is of considerable importance to the working of these stud-driving devices that the stud be driven in with its leading and trailing ends axially aligned as precisely as possible. It is also important that the driving force exerted on the stud acts centrally and axially on the trailing end of the stud. To achieve these ends, the forward end of the stud is suitably centered and axially aligned by means of a perforated disc 19 on the stud shaft. In place of discs, the studs can be anteriorly guided by jaws 4S, as shown in FIGURE 8. The jaws can be moved sideways and are complementarily recessed to form a guiding aperture to receive the stud.

Other guiding means, in combination with and to the rear of a disc 19, may be provided, as shown in the two illustrative embodiments of FIGURES a and 5b. In the upper drawing, a central lug 46 is provided in leading end 3a of a piston. In the lower drawing, lug 47 projects from the rear end of the stud itself. In FIGURE 1, a similar lug is shown as a conical centrally-mounted lug which is received into a recess of a corresponding shape in the leading end 14 of hammer 13.

Suitable embodiments of studs designed for use in the devices of the invention are shown in FIGURES 11 and l2. These studs characteristically have a perforated disc 19 mounted thereon, at or near their point 4S, and at the same time have a lug on that end which receives the driving force. This lug may be centrally mounted, for example in the form of a spherical dome 49, a cone Si), or a truncated cone. With studs having threaded heads, 'the lugs preferably are of smaller diameter than the diameter of the thread core. Another advantageous embodiment of an anchoring stud has a shaft which is slightly conically tapered, at least along a length equal to its depth of penetration. In such cases, the apex angle of the cone should be no more than 4, preferably only between 1 and 1.5.

The present invention for the first time realizes a construction of stud-driving apparatus by which anchoring studs can be driven into hard materials by means of expanding gases in a practically noiseless manner and without recoil. Further, the devices of the invention are easily convertible to manual operation by a a simple exchange of the piston therein. Also the devices offer maximum security and permit the use of a minimal propellant charge. The devices can be used as simple hand tools in crowded spaces, and optionally can be manually operated. Studs of types not previously adapted to use with propellant charges can now be used, eg. bolts of small diameter, short, or particularly, long bolts of such type.

In order to achieve maximum security, even in cases of accidental tiring, the exemplary embodiments shown in FIGURES 13-16 are equipped with a safety mechanism by means of which a stud shot from the guide tube of the stud-driving apparatus is intercepted, except when the apparatus is in position with its base placed against a surface.

In the example shown in FIGURES 13 and 14, a hinged bent arm 53 is mounted, in the axial plane of guide tube 1a, on base plate 2911. Arm 53 is moved automatically by spring 54 into the safety position shown in FIGURE 13 and held in this position by the spring. As shown in FIGURE 14, when base plate 29b is placed against the surface of material 21, arm 53 is swung into a position leaving a free path for the driving of a stud. In the safety position shown in FIGURE 13 stud 15 with its associated perforated disc 19 is intercepted in funnel-shaped opening 55 in arm 53. Opening 55 is coaxial with guide tube 1a.

The safety device shown in FIGURES 15 and 16 is constructed according to the same principle. However, in these figures arm 56 having a funnel-shaped opening 55a is fastened on a shaft 57 mounted parallel to the longitudinal axis of guide tube la. Shaft 57 is movable in an axial direction by compression of a spring 58 and such compression automatically causes a rotation of the shaft since shaft 57 is outtted with a pin 59 fitting into a corresponding helical track 60 in casing 61. In this arrangement arm 56 and opening 55a constitute a safety device which remains in safe condition until, by placing the apparatus in position against a surface, pressure on end 62 of shaft 57 pushes back arm 56. The new position of arm 56 is indicated in FIGURE 16 by the broken lines.

FIGURES 17 and 18 show a funnel-shaped enlargement 63 of the cavity in the leading end 14b of hammer 13b, which cavity serves for the reception and centering of the rear end of anchoring stud 15. With such construction, studs which are put into the driving device without a perforated disc 19 thereon Will take a skewed position as shown in FIGURE 18. Such a skewed position of the anchoring stud prevents a complete penetration of the material by the stud in cases where the perforating disc has been forgotten.

In the apparatus shown in FIGURE 19 the closed cavity Sb adjoining cartridge recess 11b terminates in a radial cavity 64. This cavity is located in a portion 65 of piston 2c having a smaller diameter than other portions of the piston. A casing 66 slides over this constricted portion 65 of the piston and covers the entrances of radial cavity 64. Casing 66 extends into closing member 5a but is restricted in its movement by a friction ring 67. Portion 65 o-f the piston may be moved down with respect to casing 66 by a blow against cap 7, until the cap engages the top of the casing. On the other hand, if the piston is moved upwards its shoulder 68 ultimately will strike the lower edge of the casing and carry the casing with it.

When the piston is positioned in the apparatus with the upper rim of casing 66 against cap 7, e.g. when the piston is in its lowermost position with end 14 of hammer 13 extending out beyond plate 29, the entrances of radial cavity 64 are not covered by the casing. Thus even if the cartridge is fired as by an inadvertent blow on the end 1 4 of the hammer, the propellant gases may expand out through the cavity soy that no injury will result. However, when a stud is inserted in leading end 14 of hammer 13 and these members as well as piston 2c are moved upwards (as shown), the entrances of radial cavity 64 are closed by casing 66. In this position the expanding gases can exert their full effect because, with friction ring 67 holding casing 66 in place, this casing is positioned to close off the entrances when the apparatus is placed against a surface.

An accidental firing can be completely excluded by means of a still further precaution. In the embodiment shown in FIGURE 20 this is achieved in part by locking the hammer 13e, which carries tiring pin 18a, in such a manner as to prevent rotary motion of the hammer. This locking is accomplished by means of radial pin 68 which slides in axial recess 69 of guide tube 1a. Piston 2d, in the forward end of which is cartridge recess 11C, is on the other hand rotatable in a limited arc with respect to axially movable casing 70 which serves as a handle. The safety position is that in which coil spring 71 lifts up plate 72 seated in the upper portions of casing 70. In this position pin 76 (see also FIGURE 2l) which ts if into a conical hole in plate 72 is released. rlorsion spring 73, one end of which is joined with head member 77 of the apparatus and the other end oi which is joined to the cylindrical extension 73 of coupling disc 74, thereupon brings about a rotation of for example 90 degrees. This rotation is imparted to piston 2d by means of non-circular opening 75 which is shaped to correspond to a section through piston 2d. When the piston is so rotated, the ilange portions which protrude down from opposite sides of the forward end ot the piston will be positioned opposite the raised central part of the hammer (see also FIGURE 22) which carries the firing pin. Thus if cap 7 is struck, these side flanges on the end of the piston will strike the central part of the hammer and thereby prevent any contact between the cartridge and the firing pin.

If the apparatus is now held manually by gripping casing 79 with base plate 29 pushed against a surface, and cap 7 with piston 2d is rotated back` to operative position against the pressure of torsion spring 73, casing 7d can be moved down into the position shown in FGURE 20. That is, the side Jilanges on the forward end of the piston will move into the regions along the sides of the raised central part of hammer lc, it being noted that these ilanges and the raised part of the hammer are formed with straight surfaces which, in this rotational position of the piston, are side-by-side and arranged to provide clearance for this downward movement of the piston. Thus the cartridge l2 will be in position to be engaged by tiring pin 13a when the cap 7 is struck.

By means ot these safety provisions an accidental firing is avoidable if the apparatus should by chance fall to the floor. A free ring of the device is avoided because cooking of the apparatus can occur only by rotating cap 7 and pushing downward on casing '70.

In FIGURES 23 and 24 are shown an embodiment in which it is impossible to strike massive cap 7 it the base plate of the apparatus is not pressed against the surface of a hard material. The safety mechanism consists of cap 79 which can be pushed axially along a portion of the apparatus. ln its extreme position cap 79 covers cap 7 and piston 2e as shown in FIGURE 23. In this position it is impossible to transmit a blow to cap 7 except with a pointed object. Also if the apparatus should fall to the floor no blow would be transmitted to cap 7. Cap 79 is automatically moved into the safety position by means of the coil spring S2. t is held in this position by locking arm 81 biased by spring Sil. When the apparatus is used, cap 79 is gripped with the hand and at the same time locking arm 81 is disengaged by pressing on lever portion 83. Cap 79 can now be slid along casing Srl into a position as shown in FIGURE 24 in which position cap 7 extends through opening 85 provided at the topmost portion of cap 79.

I claim:

l. In an explosively-actuated tool of the character described for driving studs of various lengths into a work piece consisting of hard material, first means having a work engaging surface and a stud receiving bore with an open mouth at the lower end thereof, second means extending up from and fixed to said iirst means and having an elongated cylindrical piston bore of uniform crosssection in axial alignment with said stud bore, a piston member axially slidable within said piston bore, said piston member having a portion projecting out of said piston bore adapted to receive a manually struck blow on an upper end thereof, a hammer member in said piston bore below said piston member, said hammer member being slidable in said piston bore for movement with said piston member, said hammer member having a driving end to contact the rear end of a stud in said stud bore with its tip in position to contact the work; one ot said slidable members having a recess to receive a cartridge with its base adjacent the other member, said other member having firing means to impact against said cartridge base to fire the cartridge upon said piston member being struck while a stud is in said stud chamber with its tip against the work, thus explosively forcing said hammer member toward said lower end to drive said stud into the work; said piston bore providing guide means to accommodate axial movement of both said members and said cartridge as a unit into firing position and to guide said hammer member to drive the stud into the work following the firing of said cartridge.

2. An explosively-actuated stud-driving tool comprising rst means having a piston bore of uniform crosssection, second means having a stud bore aligned with said piston bore, a piston member slidably mounted in said piston bore, and a hammer member slidably mounted in said piston bore for movement with said piston member, said hammer member having a portion extending into said stud bore to contact the rear end of a stud therein, one of said members being formed with a receptacle to receive a cartridge adapted to be iired upon sharp impact with the other of said members, whereby said hammer member portion is forced by the explosion of the cartridge through said stud bore to drive the stud into the work.

3. A tool as claimed in claim 2, wherein the crosssectional area of said stud bore is smaller than that of said piston bore, the end of said piston bore deiining a stop means for limiting movement of said hammer member, said hammer member portion extending through and beyond said stud bore when said hammer member is against said stop means.

4. A tool as claimed in claim 3 wherein said stop means consists of a replaceable disc having an aperture through which said hammer member portion can freely pass.

5. A tool as claimed in claim 2, including a iirst stop means for limiting forward movement of said hammer member portion in said stud bore, and a second stop means for limiting the forward movement of said piston member, said hammer and piston members being out of firing engagement when both are against the respective stop means.

6. A tool as claimed in claim 2, wherein said one member also is formed with an expansion chamber communieating with the inner end of said cartridge receptacle, said expansion chamber being cylindrical in shape and having a diameter smaller than said cartridge receptacle.

7. A tool as claimed in claim 2, wherein said stud bore consists of an elongated cylindrical passage through which a washer element mounted on the stud can freely pass, and at least one magnet mounted adjacent the side wall of said passage to hold the washer in place opposite the magnet.

8. A tool as claimed in claim 7, including two magnets disposed adjacent said passage side wall, said magnets being located in diametrically opposite positions about said stud bore.

9. A tool as claimed in claim 2, wherein said hammer member consists of a main body slidably engaged in said piston bore, said hammer member portion being coaxial with said main body, said main body being tightly fitted in said piston bore to seal off the explosive gases from the tiring of said cartridge.

10. An explosively-actuated stud-driving tool comprising tubular guide means having a piston bore of uniform cross-section, means having a stud bore aligned with said piston bore and having an open mouth at one end thereof to be positioned against the work into which the stud is to be driven, a piston member slidable in said piston bore, a hammer member slidable in said piston bore between said piston member and said stud bore, said hammer member having a driving end to contact the rear end of a stud in said stud bore, one of said members having a recess to receive a cartridge adapted to be fired upon sharp impact with the other of said members; said piston bore of said tubular guide means presenting a guide surface effective to guide said hammer member from its tiring position in contact with said piston member down through said stud bore to a position where its driving end is adjacent said open mouth.

11. A tool as set forth in claim 10, wherein said piston member includes a portion extending out of said tubular guide means, and a heavy recoil damping member secured to said piston member portion and having a cross-sectional area substantially larger than the cross-sectional area of said piston bore, the mass of said recoil damping member and said piston member being substantially greater than the mass of said hammer member.

12. A tool as claimed in claim 11, wherein said recoil damping member is releasably secured to said piston member, whereby different damping members can readily be substituted to accommodate different stud-driving conditions.

13. A tool as claimed in claim 10, including a cylindrical casing surrounding said tubular guide means to serve as a handle grip during operation of the tool, said casing being spaced a slight distance from said tubular guide means and arranged to form an enclosed gas expansion chamber, and vent means near the end of said piston bore adjacent said stud bore, said vent means establishing communication between said piston bore and said gas expansion chamber to permit passage therethrough of the gases from the firing of said cartridge when said driving end of said hammer member is adjacent said open mouth.

14. An explosive power assisted hammer driven tool for driving an element such as a nail, pin or stud into material comprising a body having a cylindrical bore therethrough, a cartridge plunger and a drive plunger slidably mounted in said bore and adapted for independent reciprocating movement therein, one end of said cartridge plunger extending out of one end of said bore and being adapted to be hammer driven toward the drive plunger, the other end of said cartridge plunger having cartridge holding means therein for holding a cartridge with the detonator end thereof opposed to said drive plunger and with the detonator end extending toward said drive plunger a short distance from the other end of the cartridge plunger, the drive plunger being movable toward the other end of said bore for only a limited distance and having an abutting surface at the one end thereof opposed to said cartridge plunger for tiring the cartridge upon percussive contact of the detonator end thereof with the said abutting surface and being adapted at its other end to operatively engage the element to be driven, whereby when an element is operatively engaged in the drive plunger and disposed against the workpiece, the

cartridge plunger when hammer driven with suficient force to cause the cartridge to yield and thereafter bring the detonator end of the cartridge into percussive contact with the said abutting surface detonates the explosive charge and drives the drive plunger for the extent of its limited movement, and the element is forced into the material a distance substantially corresponding to the said limited movement of the drive plunger.

15. An explosive power assisted hammer driven tool for driving an element such as a nail, pin or stud into material comprising a body having a cylindrical bore therethrough, a cartridge plunger and a drive plunger slidably mounted in said bore and adapted for independent reciprocating movement therein, one end of said cartridge plunger extending out of one end of said bore and being adapted to be hammer driven toward the drive plunger, the other end of said cartridge plunger having cartridge holding means therein for holding a cartridge with the detonator end thereof opposed to said drive plunger, the drive plunger being movable toward the other end of said bore for only a limited distance and having an abutting surface at the one end thereof opposed to said cartridge plunger for firing the cartridge upon percussive contact of the detonator end thereof with the said abutting surface and being adapted at its other end to operatively engage the element to be driven, whereby when an element is operatively engaged in the drive plunger and disposed against the workpiece, the cartridge plunger when hammer driven with suflicient force to cause the cartridge to yield and thereafter bring the detonator end of the cartridge into percussive contact with the said abutting surface detonates the explosive charge and drives the drive plunger for the extent of its limited movement, and the element is forced into the material a distance substantially corresponding to the said limited movement of the drive plunger.

References Cited in the rile of this patent UNITED STATES PATENTS 2,724,116 Termet Nov. 22, 1955 2,790,173 Henning et al. Apr. 30, 1957 2,950,481 Skumawitz Aug. 30, 1960 FOREIGN PATENTS 149,829 Sweden Apr. 26, 1955 166,735 Australia Jan. 31, 1956 204,458 Australia Nov. 21, 1956 744,822 Great Britain Feb. 15, 1956 772,351 Great Britain Apr. 10, 1957 

1. IN AN EXPLOSIVELY-ACTUATED TOOL OF THE CHARACTER DESCRIBED FOR DRIVING STUDS OF VARIOUS LENGTHS INTO A WORK PIECE CONSISTING OF HARD MATERIAL, FIRST MEANS HAVING A WORK ENGAGING SURFACE AND A STUD RECEIVING BORE WITH AN OPEN MOUTH AT THE LOWER END THEREOF, SECOND MEANS EXTENDING UP FROM AND FIXED TO SAID FIRST MEANS AND HAVING AN ELONGATED CYLINDRICAL PISTON BORE OF UNIFORM CROSSSECTION IN AXIAL ALIGNMENT WITH SAID STUD BORE, A PISTON MEMBER AXIALLY SLIDABLE WITHIN SAID PISTON BORE, SAID PISTON MEMBER HAVING A PORTION PROJECTING OUT OF SAID PISTON BORE ADAPTED TO RECEIVE A MANUALLY STRUCK BLOW ON AN UPPER END THEREOF, A HAMMER MEMBER IN SAID PISTON BORE BELOW SAID PISTON MEMBER, SAID HAMMER MEMBER BEING SLIDABLE IN SAID PISTON BORE FOR MOVEMENT WITH SAID PISTON MEMBER, SAID HAMMER MEMBER HAVING A DRIVING END TO CONTACT THE REAR END OF A STUD IN SAID STUD BORE WITH ITS TIP IN POSITION TO CONTACT THE WORK; ONE OF SAID SLIDABLE MEMBERS HAVING A RECESS TO RECEIVE A CARTRIDGE WITH ITS BASE ADJACENT THE OTHER MEMBER, SAID OTHER MEMBER HAVING FIRING MEANS TO IMPACT AGAINST SAID CARTRIDGE BASE TO FIRE THE CARTRIDGE UPON SAID PISTON MEMBER BEING STRUCK WHILE A STUD IS IN SAID STUD CHAMBER WITH ITS TIP AGAINST THE WORK, THUS EXPLOSIVELY FORCING SAID HAMMER MEMBER TOWARD SAID LOWER END TO DRIVE SAID STUD INTO THE WORK; SAID PISTON BORE PROVIDING GUIDE MEANS TO ACCOMMODATE AXIAL MOVEMENT OF BOTH SAID MEMBERS AND SAID CARTRIDGE AS A UNIT INTO FIRING POSITION AND TO GUIDE SAID HAMMER MEMBER TO DRIVE THE STUD INTO THE WORK FOLLOWING THE FIRING OF SAID CARTRIDGE. 